Grinding helicoidal surfaces



Feb. 4, 1928.

E. WILDHABER GRINDING HELICOIDAL SURFACES Filed July 15, 1923 2 Sheets-Sheet 1 INVENTOR. 1" BY m W14.

A TTQRNEY.

Feb. 14, 1928.

E. WILDHABER GRINDING HELICOIDAL SURFACES Filed July 13, 1923 2 Sheets-Sheet 2 INVENTOR.

6 7/ ATTORNEY.

Patented Feb. 14, 1928.

UNITED STATES 1,659,227 PATENT emery I nnNnsT WILDHAIBEB, OFlBROOKLYiN, NEW YORK, Ass IGNoB. 'ro ILES-BEMEN'r-PQND COMPANY, or NEW YORK, N. Y., A. CORPORATION on NEW JERSEY.,

GRINDING HELICOIDAL SURFACES.

Application filed July 13, 1923. Serial No. 651,394.

thread to involute helicoids in an efficient manner.

Another object of my invention is to pro vicle a method of the above indicated character for grinding a worm thread by the flat side of a grinding wheel in such manner that only one angular setting of the wheel is required in order to grind involute helicoids on the sides of the thread.

A further object of my invention is to pro-- vide amethod that shall" grind involute heli coids on the sides of worm threads by means of a grinding wheel having a flat grinding. surface, the grinding wheel being angularly adjusted-about an axis in the direction of the shortest line between the axis of the wheel and the axis of the worm in accordance with the involute helicoids, and the wheel, if necessary,'being adjusted horizontally and ye'r tically to effect correct engagement between the wheel and the/ blank.

It is customary, at the present time, to grind involute helicoids on the sides of a worm thread by means of a grinding wheel having its. axis in the plane of the shortest line between the axis of the wheel and the axis of the worm being ground. In such case it .is necessary, in order, to grind involute helicoids, to angularly adjust the grinding wheel not only about a'sin'gle axis, but also to angularly adjust the grinding wheel about a second axis normal to the first. Each an 'gular adjustment mustbe made very accurately, inasmu'chas theaccuracy of the involute helicoid bein cut depends upon the accuracy of such adwstments.

In forming involute helicoids on. the sides.

of worm threads in, accordance with m method, the grinding wheel is angularlya justed about only one-axis, namely an axis in the direction of the shortest di'stancebetween the' blank .axis and the wheel axis. Preferably the. shortest'line between the blank axisanclthemheel axis is, located in a horizontal plane. The angularadwstment about such axis must be"accuratelymade,

inasmuch as the helieoid cut is depend-- ent upon the angle at which the grinding surface is set. The grinding wheel is adjusted in a vertical plane and also in a horizontal plane. However, the vertical and the hori-, A- zontal ad ustments do not need to be made an with the accuracy of the angular adjustment. The vertical and the horizontal adjustments effect only the fillet formed at the bottom of the Worm thread.

In the accompanying drawings:

Figure 1 is a plan view of a grinding Wheel in engagementwith a worm.

Fig. 2 is an end elevational view of the worm and wheel shown in Fig. 1.

Fig. 3 is a diagrammatieplan VIGW'OIE a grinding machine adapted to operate in accordance with my invention.

.Fig. 4 is a front elevational view of the 1 machine shown in Fig. 3.

Referring to Figs. 1 and 2 of the drawings, a grlndingi wheel 1 is shown in engagement with the tiread 2 on a worm 3. The worm 3 is assumed to rotate on an axis c-0 and the grinding wheel 1 is assumed to rotate on an axis 0' 0. The wheel shown is a cupso shaped grinding wheel having an annular grinding ring extending betweenthe limit* ing circles 4 and 5,,a's best shown in Fig. 2

of the drawings. The grinding surface is perpendicularl disposed with respect to the 5 axis 0'c oft e grinding wheel. Inasmuch as only an annular ring near the edge of a flat (grinding Wheel is utilized during the grin ing operation, it..is considered in the present invention that a cup-shaped grinding wheel is the equivalent of a grinding wheel having a flat grinding surface.

An involute helicoidal surface may be considered as composed of a number of straight lines which are all tangent to a predetermined helix. Moreover, tangential planes may be drawn with respect to the involute helicoidal surface-which contacts with the surface'not merely at a point, but in a straight line. plane may be placed in such a tangential) plane to an involute helicoid for grinding the involute helicoid.- For a more complete explanation as to the properties of an involute involutehelicoidal surface always produces 110 i Consequently a grinding o 'helicoid, reference may be made to my colute has the same diameter as the helix upon which the involute helicoid is formed and in other words the base cylinder of the involute helicoidal surface is identical with the cylinder onwhich thehelix is wound.

In Fig. 2 of the drawings, the base cylinder of the involute helicoid is indicated by a dot-and-dash circle Z). The line 67 alon which the grinding wheel engages a threa of the worm is indicated in Figs. 1 and 2 of the drawings. Such line 67, it will be apparent, is tangent to the base circle I) in order to form an involute helicoid on the side of the worm thread. The depth circle 9 or the bottom of the worm thread 2 is indicated in Figs. 1 and 2 of the drawings. As heretofore set forth it is to be understood that the grinding surface on the wheel 1 is perpendicularly disposed with respect to the axis o-c.

In Fig. 2 of the drawings, it will be noted the axis of the grinding wheel 1 is elevated abovethe axis of the worm 3. If two lines such as the axis c-cof the worm 3 and the -axis c'-c of the wheel do not intersect, theIT effecting longitudinal feeding of the worm in the shortest connectin line between the two axes must be a perpen icular line connecting them. In Figs. 1 and 2 of the drawings, the shortest connecting line between theaxis c-0 and the axis c-c isindicated by the reference character 10. In Fig. 2 the dotted line 11 is assumed to indicate the position of the grinding wheel 1 when so set that the.in

tersection point of the grinding surface and the axis of the grinding wheel is in' the line 10. The line 10 is assumed to be the shortest distance between the axis c-c.and the axis c'-c. In the position of the wheel, as indicated by the dotted line in Fig. 2 of the drawings, the grinding whc 31 extends to the base circle 9 and the axis of the grinding wheel is in .the position cc". In such position of the grinding wheel, it will be noted only a very small portion of the line 6-7 is covered by the grindin surface. Accordingly, in order to grind a ong the line it will be necessary to advance. the grinding wheel towards the axis cc of the worm. In advancing the grinding wheel towards the blank axis, a distance such that the line 6-7 will be covered by the grinding wheel, a very deep fillet would be formed at the bottom of the worm thread. Accordingl it would be impractical to grind a worm a grinding wheel which is only adjusted a out the line of shortest distance between the axis of the blank and the axis of the wheel.- As heretofore set forth, it is possible to effect a second angular adjustment of the wheel about a vertical axis as the parts are disposed v1n Figs. 1 and 2, but such adjustment must be effected with extreme accuracy.

In order to grind along the line 6-7 and not be compelled to efiect a second angular adjustment of the grinding wheel, the grinding wheel may be raised above the axis of the worm and then moved towards the worm to the osition indicated by full lines in Fig.2 of t e drawings. In describing the position of the grinding wheel with respect to the worm, it has been assumed that the grinding axis c-c and the worm axis c-c are initially in a horizontal plane. In such case the angular adjustment of the wheel would necessarily be about an axis in,the direction of the line 10 which is a horizontal line connect; ing the axes c--c and cc. The wheel axis 'is raised vertically and is moved horizontally towards the worm until a position is reached as indicated in Fig. 2 of the drawings by the Referring to Figs. 3 and 4 of the drawings, a machine for grinding a worm in accordance with my invention is diagrammatically illustrated. In Figs. 3 and 4 of the drawings, a grinding wheel 15 is shown in engagementwith a'thread 1 6 on a worm 17 The worm 17 is mounted on a spindle 18, which is rotated in any suitable manner. Any suit able means (not shown) may be provided for accordance with the rotation thereof. The worm and sp ndle are supported on a slide 19 which is longitudinally movable on a slide 20. The slide 19, as shownin Figs. 3 and 4, is movable longitudinally with respect to the machine.- The slide 20 is directly,mo unted on the frame 21 of the machine and is moved by. means of a er and rack mechanism 22, as indicated in ig. 4 of the drawings. .The

slide 20 is moved transversely with respect to.

the machine and mayserve not only to bring the blankor worm'into enga ement with the grinding wheel, but also, permit indexing under certain conditions.

The grindin wheel 15 is mounted on a shaft 23 whic is rovided with suitable bearings on a base p ate 24. The base plate 24 is rotatably mounted on a vertical slide 25. Any suitable means may be provided for angular-1y adjusting theposition of the base plate 24. In Figs. 3 and 4. of the drawings, a worm and worm wheel mechanism 26 is shown for adjusting the angular position of the base plate. It is. to be understood that the base late 24 is adjusted about an axis which is perendicular to the axis of the grinding wheel. ,Fi 3 of the drawings, it is apparent that t e axis d/d is perpendicular to the axis of the grinding wheel. In Fig. 4 of the drawings, it will be noted the pro ection of the axis M is perpendicular to the axis of the worm.

The vertical slide 25,- which is-mounted on a portion 27 of the machine. is moved by means of any suitable mechanism, as for example, a bevel gear mechanism 28.

In grinding 'a worm in accordance with if so desired, to

my method, the grinding wheel is anguhGllCOld WhlCll isto be cut on the sides of the worm thread. The vertical slide 25 is adjusted in order that the grinding wheel may cover the-contact line on the worm thread as indicated inlFigs. 1 and 2 of the drawings. The slide is then operated to move the worm into engagement with the' grinding wheel. No means has beemshown for advancing the slide 19 in actordance with the rotation of the worm and the pitch of the worm thread, inasmuch as such mechanisms are well known.

The grinding wheel 15 is operated in any suitable manner, as by means of an electric motor 30. The motor 30 is mounted on the plate 24: and carries a pulley 31 which is connected by a belt 32 to a pulley 33 which is mounted on the shaft 23.

, It will be understood that such changes and modifications may be made in my invention as fall within the limits of the appended claims.

What I claim is:

1. The method --of grindin an involute helicoidal surface on a blank, which consists in providing a grinding wheel having a flat grinding surface, in effecting an angular adjustment and two rectilinear ad ustments between the wheel and the blank so that the shortest connecting line between the axis of the blank and the axis of the wheel is outside the surface of the grinding wheel, and in rotating the wheel and the blank while effecting relative feeding movement in accordance with the pitch of the helicoid.

2. The method of grinding an involute [helicoidal surface on a blank, which consists in providing a gr nding wheel having a flat grinding surface, in positioning the axis of the blank and the axis of the wheel in parallel relation, in effecting one angular adjustment of the wheel and two rectilinear adjustments between the wheel and the blankso that the shortest' line between the axis of the blank and the axis of the wheel is outside the surface of the grinding wheel, and in rotating the wheel and the blank while effecting relative feeding movement in accordance with the pitch of the helicoid.

,3. The method of grinding an involute helicoidal'surface on a blank, which consists in providing a grinding wheel having a fiat grinding surface, in positioning the axis of the blank, and the axis of the wheel in parallel relation, in angularly adjusting the grinding wheel" about an axis extending in the direction of the shortest distance between the axis of the wheel and the axis of the blank, in effecting rectilinear adjustments perpendicularly and parallelly-to the shortest distance between the axis of the .wheel and the axis of the blank, and in re 4. The metho'dof grinding an involute helicoidal surface on a blank, which consists in providing a grinding wheel having a flat grinding surface, in angularly adjust-mg the wheel about an axis parallel to a line per,- pendicular to the blank axis, in effecting rectilinear adjustments between the wheel and the blank perpendicularly and parallelly to the shortest connecting line between the wheel axis and the blank axis, and in r0,- tating the blank and the wheel while effecting relative feeding movement in accordance with the pitch of the helicoid.

5. The method of grinding an involute helicoidal surface on a blank, which consists in providing a grinding wheel having a flat grinding surface, in positioning the axis of the blank and the axis of the wheel in paral lel relation, in angularly adjusting the wheel about an axis extending in the direction of the shortest line .between the axis of the wheel and the axis of the blank, in relatively adjusting the wheel and the blank in a direction perpendicular to said shortest line, and in rotating the wheel and the blank while effecting relative movement inaccordance with the lead of the helicoid.

6. The method of grinding an involute helicoidal surface on a blank, which consists in providing a grinding wheel having a flat grinding surface, in positioning the axis of 109 the blank in a horizontal plane, in angularly adjusting the grinding wheel in accordance with the lead of the helicoid about a horizontal axis perpendicular to the axis of the blank, in relatively adjustin the blank and 105 the wheel in a horizontal p ane, in adjustin the blank and the wheel While effecting re ative feeding movement in accordance with the pitch of the helicoid.

7. The method of grinding an involute helicoidal surface on a blank, which consists in providing a grinding wheel havinga flat grinding surface, in positioning the axis of the wheel and the axis of the blank in parallel relation, in angularly adjusting the grinding wheel in accordance with the lead of the helicoid about an axis parallel to a line perpendicular to the axis of the blank, l

in relatively adjusting the wheel and the blank towards and away from each other, in adjusting the axis of the wheel perpendicularly to a line perpendicular to the blank axis, and in rotating the wheel andtheblank while effecting feeding movement'in accordance with the pitch of the helicoid.

8. The method of grinding an involute helicoidal surface on a blank, which consists in providing a grinding wheel having a flat .130

grindin surface, in a ngularly adjusting the wheel a out an axis parallel to a line perendicular to the axis of the blank, in adusting the blank and the wheel away from 5 and towardeach other, in adjusting the wheel \axis with respect to the blank axis in a plane perpendicular to the axis of angular emma? ERNEST WILDHABER. 

